subtle shuttering when accelerating on a brand new engine

suprascoot · 07-18-2007, 03:02 AM

I've just finished doing a complete rebuild on my 89T and it is running damn near perfect accept for some subtle shuttering when i'm accelerating. Its most predominant in 2nd and 3rd around 2000 RPM. It almost feels like a inconcistent miss. Idle sounds and feels perfect. Been told it may be my valves not having fully set yet since the head was completely worked during the rebuild. Checked timing again and again. I just have no clue what it could be and kinda frustrated. Any Help Please?????

cre · 07-19-2007, 06:09 AM

It shouldn't be the valves. If the valves weren't touched when the head was machined, but they were removed and not replaced in the same place and rotation they were in when removed they may be leaking... this isn't something that goes away on it's own. If you had a valve job done they should seat perfectly. Do a compression test if you really think the valves aren't sealing. Did you verify all the valve shim clearances?

As for timing, are you checking the ignition timing or the physical timing of the engine? The timing belt may be off by one tooth on one of the cams or the CPS/distributor drive gear.

Also make sure you're getting a strong spark to each cylinder and make sure all of the engine/ECU/battery grounds are clean and secure.

west_side_supra · 07-24-2007, 11:27 AM

id check the spark plugs and also the Coil pack's and harness for melted wires, same thing with the CPS wires

07-18-2007, 03:02 AM	#1
suprascoot Stock Join Date: Jul 2007 Location: tennessee Posts: 12	subtle shuttering when accelerating on a brand new engine I've just finished doing a complete rebuild on my 89T and it is running damn near perfect accept for some subtle shuttering when i'm accelerating. Its most predominant in 2nd and 3rd around 2000 RPM. It almost feels like a inconcistent miss. Idle sounds and feels perfect. Been told it may be my valves not having fully set yet since the head was completely worked during the rebuild. Checked timing again and again. I just have no clue what it could be and kinda frustrated. Any Help Please?????

07-24-2007, 11:27 AM	#3
west_side_supra 12psi boost Join Date: Sep 2006 Location: Marysville Washington Posts: 353	id check the spark plugs and also the Coil pack's and harness for melted wires, same thing with the CPS wires __________________ 7MGTE - 500hp never dyno'd exhaust: 3inch pipes no cat/powerhouse manifold/garret gt47 18psi/HKS SS racing wastegate fidenza cam gears intake: PHR 4inch intake/K&N filter/3 inch intercooler/ pipeFMIC/greddy type R bov/ fuel: 550cc PTE/ walbro 255lp / Aeromotive adj pressure regulator transmission: Fidenza flywheel/ACT extreme kit electronics: map ecu 1 / HKS EVC 9 gauges:boost,EGT,oil temp & pressure/aem AFR

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07-19-2007, 06:09 AM	#2
cre Toyota Racing Development Join Date: Apr 2007 Posts: 5,038	It shouldn't be the valves. If the valves weren't touched when the head was machined, but they were removed and not replaced in the same place and rotation they were in when removed they may be leaking... this isn't something that goes away on it's own. If you had a valve job done they should seat perfectly. Do a compression test if you really think the valves aren't sealing. Did you verify all the valve shim clearances? As for timing, are you checking the ignition timing or the physical timing of the engine? The timing belt may be off by one tooth on one of the cams or the CPS/distributor drive gear. Also make sure you're getting a strong spark to each cylinder and make sure all of the engine/ECU/battery grounds are clean and secure.